1. Field of the Invention
This invention relates to a novel process for the removal of arsenic from aqueous systems containing competing ions utilizing an improved absorbent material.
2. Description of Related Art
Arsenic, classified by the EPA as a Class A carcinogen, is the 20th most abundant element in the earth's crust. As a result, arsenic contamination of drinking water sources is common, particularly in the western United States.
The removal of arsenic from water by adsorption is generally known in the art. See, for example, J. H. Gulledge and J. T. O'Connor, "Removal of Arsenic (V) from Water by Adsorption on Aluminum and Ferric Hydroxides," Water Technology/Quality Journal AWWA, August, pages 548-552 (1973) and M. A. Anderson, J. F. Ferguson and J. Gavis, "Arsenate Adsorption on Amorphous Aluminum Hydroxide," Journal of Colloid and Interface Science, Vol. 54, No. 3, March (1976).
Also, D. Clifford and C. Lin, "Arsenic (III) and Arsenic (V) Removal from Drinking Water in San Ysidro, N.M.," U.S. EPA Project Summary--EPA/600/S2-91-011 June (1991), report results of using activated alumina for the removal of arsenic from drinking water.
S. K. Gupta and K. Y. Chen, "Arsenic Removal by Adsorption" Journal WPCF, pages 493-506, March 1978, report using activated alumina, activated bauxite and activated carbon as adsorbents for arsenic in water.
U.S. Pat. No. 4,935,146 describes a method for reducing the amount of a first contaminant and second contaminant in a solution to environmentally safe levels, said solution having a substantially greater amount of the first contaminant than the second contaminant. The method comprises: contacting the solution with an activated or calcined product of a compound having the formula A6B2(OH)16C.4H20, wherein A is a divalent metal cation, B is a trivalent metal cation and C is a mono- to tetravalent anion. The method further comprises separating the solution from the contacted product.
It is anticipated, however, that the EPA's current maximum concentration limit for arsenic in drinking water of 50 micrograms per liter (50 parts per billion) will be reduced to below 10 micrograms per liter, as already has been done (1995) by the World Health Organization.
In view of these likely more stringent EPA regulations for arsenic, there is still a need for adsorbent materials which are effective at removing arsenic levels to lower than ten parts per billion and which have arsenic loading level capabilities suitable for use in commercial applications.